JPH01217363A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance mechanical strength and abrasion resistance of a photosensitive body and to improve printing resistance by heat hardening a specified lower alkylpolysilsesquioxane and using it as a surface protective layer. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate a photoconductive layer and the surface protective layer obtained by heat hardening the lower alkylpolysilsesquioxane represented by formula I in which R is methyl or ethyl, having a weight average molecular weight of 10<3>-10<7> and fine inorganic oxide particles may be added to this surface layer, thus permitting excellent durability and printing resistance never obtained so far in organic photosensitive bodies to be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a bioelectrophotographic photoreceptor, in which a photoconductive layer 1 and a surface protective layer are successively formed on a conductive support. The lower alkyl polysilsesquioxane having a weight average molecular weight of 103 to 107 is thermally cured.

[Industrial application field]

The electrophotographic photoreceptor of the present invention can be widely applied to copying machines, printers, and the like.

The electrophotographic process consists of the steps of charging, exposing, developing, transferring, and fixing, and prints are obtained by repeating these steps. Charging applies a uniform positive or negative electrostatic charge to the surface of a photoconductive photoreceptor. In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoreceptor by irradiating it with laser light or the like to erase the surface charge on a specific portion. Next, this latent image is electrostatically developed with powder ink called toner, thereby forming a visible image of the toner on the photoreceptor. Finally, this toner image is electrostatically transferred onto recording paper and exposed to heat and light.

Then, a printed matter is obtained by fusing with pressure or the like.

[Conventional technology]

As photoreceptors for electrophotography, organic photoreceptors using organic substances are being actively developed. This is because it can be manufactured using a simple coating method, making it easy to reduce costs through mass production.Compared to inorganic photoreceptors that use inorganic substances such as selenium, this material has a wider range of material selection, so non-toxic compounds can be selected. It has the advantage of being maintenance-free by being disposed of by the user.

Generally, organic photoreceptors have lower sensitivity than inorganic photoreceptors such as selenium, but high sensitivity can now be achieved by constructing a functionally separated layered photoreceptor in which a charge generation layer and a charge transport layer are laminated. Became.

Here, the charge generation layer has the function of absorbing incident light and generating electron-hole pairs (carrier pairs), and the charge transport layer transports one of the carriers generated in the charge generation layer to the surface of the photoreceptor. It has the function of forming an electrostatic latent image. By separating the functions of the photoreceptor into two layers in this way, the optimal compound for each function can be selected almost independently, increasing sensitivity.

It is possible to dramatically improve optical characteristics such as spectral characteristics.

The charge generation layer is formed by dissolving or dispersing in a binder resin a charge generation substance that absorbs light and generates carrier pairs. Phthalocyanine pigments, azo pigments, etc. are generally used as the charge generating substance, and polyester, polyvinyl butyral, etc. are generally used as the binder resin.

Further, the charge generation layer can also be formed by vapor deposition of phthalocyanine or the like without using a binder resin. On the other hand, the charge transport layer is formed by dissolving a charge transport material that transports charge carriers in a binder resin. Charge transport material (CT
M) is an electron transport ZCTM (chloranil) which has a large electron affinity and can easily transport electrons.

bromanyl, trinitrofluorenone, etc.), and hole-transporting CTMs (pyrazoline, hydrazone, etc.) that have a small ionization potential and are easy to transport.

oxazole, etc.). Polyester, polycarbonate, etc. are generally used as the binder resin for the charge transport layer.

The surface of the photoreceptor is used by being positively or negatively charged depending on the type of photoreceptor, but if the photoreceptor is negatively charged, corona discharge becomes unstable and the photoreceptor surface is easily deteriorated by ozone generated during discharge. Positive charging is preferable. It is necessary to transport the functionally separated two-layer structure photoreceptor to the front to eliminate the positive charge on the surface. However, electron-transporting CTMs generally have problems such as carcinogenicity, and there are problems in putting them into practical use. Therefore, by forming a layer structure in which a charge transport layer is formed on a conductive support and then a charge generation layer is formed, the hole transporting CTM can be used with positive charging. Can be done.

Generally, photoconductive layers such as charge transport layers and charge generation layers are formed by applying and drying a coating solution in which the constituent materials of each layer are dissolved or dispersed in an organic solvent. The coating method is appropriately selected from among the doctor blade method, spray coating method, etc. depending on the shape of the support, etc., but the dipping method is the best in the case of a cylindrical support. This is a method to obtain a coating film on the support by immersing the support in a coating solution and then pulling it up at a predetermined speed, allowing precise film thickness control with a relatively simple device. .

To produce the above-mentioned positively charged two-layer structure photoreceptor using this method, first, a cylindrical support is immersed in a hole-transporting charge transporting layer coating solution, and pulled up at a predetermined speed. A charge transport layer is formed by drying. Subsequently, the support on which the charge transport layer has been formed is immersed in a charge generation layer coating solution.
A charge generation layer is formed by pulling and drying. In this case, since the charge generation layer generally requires an extremely thin film thickness of 1 μm or less, there is a problem that the photoreceptor characteristics change due to slight abrasion of the surface. A surface protective layer is formed using a resin solution in which additives such as inorganic oxides are dispersed, and a positively charged two-layer photoreceptor structure is obtained.

[Problem to be solved by the invention]

Electrophotographic photoreceptors are required to have desired sensitivity, electrical properties, and optical properties according to the electrophotographic process to which they are applied, and are also desired to have good moisture resistance and durability. However, as mentioned above, the surface protective layer of an organic photoreceptor is a thermoplastic resin or thermosetting resin containing an inorganic oxide.
Compared to inorganic photoreceptors, the surface hardness is lower, and when rubbed with a nylon brush or rubber blade during the toner cleaning process in the electrophotographic process, the surface is abraded and the photoconductivity changes.

Furthermore, due to frictional contact with the magnetic carrier used in the two-component developer, changes in photoconductivity due to surface abrasion are also likely to occur. This is because the surface protective layer requires a certain degree of transparency, so it cannot contain large amounts of additives such as inorganic fillers that would reduce transparency, making it impossible to obtain high surface hardness. In order to maintain the characteristics of the photoreceptor consisting of the photoreceptor layer and the charge generation layer, the film thickness must be extremely thin, so there is a considerable problem in durability. Therefore, the biggest drawback of organic photoreceptors is their printing durability, which is 1 to 1 million sheets compared to 50,000 to 300,000 sheets for selenium-based photoreceptors and 500,000 to 1 million sheets for amorphous silicon photoreceptors.
~50,000 sheets, short life span, medium speed.

Considering the application to high-speed copying machines and optical printers, there was a need for further improvements in printing durability.

[Means to solve problems]

The above problem is solved in an electrophotographic photoreceptor in which a photoconductive layer 1 and a surface protective layer are sequentially laminated on a conductive support.
This problem can be solved by using a lower alkyl polysilsesquioxane which is heat cured.

(In the formula, R represents CH3, t, or US.) Furthermore, inorganic oxide particles may be added to the surface protective layer of the present invention.

[Effect]

The lower alkyl polysilsesquioxanes of the present invention include methylpolysilsesquioxane and ethylpolysilsesquioxane, particularly those having a weight average molecular weight of 10.000 to 10.0.
It is an organic silicone polymer soluble in organic solvents having a molecular weight of 10.000 to 1.0.
00,000. If the weight average molecular weight is 10.000 or less, the crosslinking density of the thermosetting polymer becomes too high, and the film is likely to crack. On the other hand, if the weight average molecular weight is 10,000,000 or more, the crosslinking density becomes low, and a desirable value for the hardness of the cured product cannot be obtained. Also, phenyl group, aryl group such as tolyl group, or isobutyl group.

Polysilsesquioxanes having relatively higher alkyl groups such as isoamyl groups are also known (J.

8mer, chem, soc, Vo1.82. P619
4 (1960), J. Polymer Sci, Vo.
1, C-1, P83 (1963)). However, such aryl group-containing polysilsesquioxanes and higher alkyl polysilsesquioxanes have the disadvantage that they tend to crystallize when formed into a coating, making it difficult to obtain uniform film formation.

The lower alkyl polysilsesquioxane of the present invention is hydrolyzed and polycondensed to produce a prepolymer, and when this is further increased in molecular weight, (1) the step of dissolving the lower alkyl trichlorosilane in an organic solvent; A step of dropping water onto an organic solution is performed at a temperature of -20°C to -50°C, and (2) a step of dropping water onto the organic solution, and a step of dropping water below the organic solution layer. The process of heating and increasing the molecular weight while coexisting the layers of
0 cm), it is possible to obtain a lower alkyl polysilsesquioxane having a weight average molecular weight of 10,000 to 1,000,000 represented by the general formula: (wherein R represents CH3 or CtH5). can.

(JP 61-108628) Alternatively, the lower alkyl polysilsesquioxane of the present invention can be prepared by dissolving methyltrichlorosilane or ethyltrichlorosilane in a ketone-furan mixed solvent using triethylamine as a catalyst, and in the first step, this solution is was cooled on ice and water was added dropwise under normal pressure to obtain a number average molecular weight of 9.000 to 10.
000 polysilsesquioxane prepolymer was produced and precipitated with methyl alcohol. In the second step, the prepolymer was again dissolved in a ketone-furan mixed solvent, and an ammonium salt was added as a catalyst and the mixture was heated at 90°C for several seconds. The molecular weight is increased by a time reaction, and the number average molecular weight is 10,000 to 1.
It may also be a polymer of 00.000. (Unexamined Japanese Patent Publication No. 53-
88099) At this time, in the first step, the step of dissolving the lower alkyltrichlorosilane in the solvent and the step of dropping water into the resulting organic solution are performed while cooling the organic solution to -20°C to -50°C. It suppresses the reactivity of the trace amount of water dissolved in the solvent and the dripping water with lower alkyltrichlorosilane, thereby preventing three-dimensional condensation polymerization of the prepolymer, and converting the resulting polymer into an organic solvent. It is necessary to maintain the solubility of the

According to the present invention, by using lower alkyl polysilsesquioxane as a surface protective layer, surface hardness can be significantly improved compared to conventionally used thermoplastic resins and thermosetting resins containing inorganic oxides. Therefore, the surface protective layer is not scraped and worn even by the harsh cleaning conditions in the electrophotographic process or by repeated contact with a magnetic brush developer made of magnetic carrier, which is different from conventional organic photoreceptors. io that was considered impossible to achieve
It is possible to obtain a life of more than o, ooo sheets.

The photoresistance in the present invention is obtained by sequentially laminating a conductive support such as an aluminum tube, a charge transport layer on the body, and then a charge generation layer.

The charge transport layer is prepared by dissolving a binder resin and a charge transport substance in an organic solvent, adding a curing agent if necessary, and applying the mixture to a support.

It is formed by coating and heating and drying.

The film thickness is 5 to 30 μm. As the binder resin, polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic resin, polycarbonate, silicone resin, epoxy resin, etc. are used. In addition, as the charge transport substance, known compounds such as hydrazone compounds, pyrazoline compounds, and oxazole compounds can be used.As the solvent, ketone solvents such as MEK, alcohols such as ethanol, etc. can be used. Usable solvents include aromatic solvents such as toluene, chlorinated hydrocarbon solvents such as methylene chloride, ether solvents such as THF, and mixtures thereof.

The charge generation layer is formed by dispersing or dissolving a charge generation substance in a solvent in which a binder resin is dissolved, and coating the mixture on the charge transport layer and drying it. Known charge generating substances can be used, such as bisazo compounds, trisazo compounds, perylene compounds, indigo compounds, cyanine compounds, squarylium compounds, phthalocyanine compounds, etc. .

As the binder resin, polyester, polyvinyl alcohol, polyvinyl butyral, polyamide, silicone, acrylic-styrene, etc. can be used. The solvent is selected in consideration of the charge generating substance and binder resin to be used, but the same solvent as used for coating the charge transport layer can be used. The film thickness is 0.01 to 3 μm, but preferably 1 μm or less.

The surface protective layer is formed by applying, drying, and thermosetting a resin solution of lower alkyl polysilsesquioxane or a resin solution containing an inorganic oxide onto the charge generation layer.

As the inorganic oxide, fine powder (1 μm or less) of titanium oxide, tin oxide, zinc oxide, etc. is used. The thickness of the protective layer is 0.5 to 3 μm, preferably 1 to 2 μm.

Further, an undercoat layer can be provided between the conductive support and the charge transport layer in order to improve adhesion, prevent thermal carrier injection, and the like. The undercoat layer is polyvinyl alcohol or polyvinyl butyral.

Resins such as polyamide and epoxy, or resins in which additives such as tin oxide, indium oxide, and titanium oxide are added to these resins are used. The thickness of the undercoat layer is 0.0
It is 1 to 3 μm.

Hereinafter, the present invention will be explained according to examples.

〔Example〕

Synthesis example: reflux condenser, 2 dropping funnels, nitrogen blowing tube.

methyl isobutyl ketone in a reaction vessel equipped with a stir bar;
540m7! and 84 ml of triethylamine catalyst were added, and nitrogen was blown into the container to replace the inside of the container with nitrogen.

The reaction vessel was cooled to a temperature of -30°C to -40°C in a dry ice ethyl alcohol bath, and while stirring the solution,
713 mβ of methyltrichlorosilane was injected and reacted with trace amounts of water in the solvent to form a white precipitate of triethylamine hydrochloride.

While pressurizing the water column to 10cm with nitrogen gas, fishing for 100m
1 was added dropwise over 90 minutes. As a result, triethylamine hydrochloride was produced and dissolved in excess water to promote the hydrolysis reaction of methyltrichlorosilane to produce a prepolymer. Next, while keeping the two liquid layers pressurized with nitrogen gas to a water column LOcm, dry ice cooling was stopped and the temperature was gradually raised to room temperature, and then kept under pressure in the same way at 90±2℃ in an oil bath for 10 hours. The mixture was refluxed to increase the molecular weight of the methylpolysilsesquioxane.

The organic layer was separated and washed with water until the washing water became neutral to remove triethylamine hydrochloride. After removing the aqueous layer, the organic layer was concentrated by distillation, and ethyl alcohol was added as a precipitant to precipitate the polymer. The precipitated polymer was further thoroughly washed with a precipitant and then vacuum dried. As a result of infrared absorption analysis, this polymer was confirmed to be methylpolysilsesquioxane having a ladder structure, and as a result of GPC analysis, the weight average molecular weight was ioo, ooo.

Example 1: 50 parts by weight of a hydrazone compound and 50 parts by weight of polycarbonate were completely dissolved in a mixed solvent of dichloromethane and dichloromethane to prepare a charge transport layer coating solution. Next, 60
After applying the coating liquid on a φX250 mm aluminum tube using the dipping method, heat treatment was performed at 90°C for 60 minutes, resulting in a film thickness of approximately 20μ.
A charge transport layer of m was formed.

Next, 50 parts by weight of ε-type copper phthalocyanine and 50 parts by weight of polyester resin were dissolved in tetrahydrofuran and put into a hard glass pot together with hard glass beads.
The mixture was dispersed and mixed for 4 hours to obtain a charge generation layer coating solution. A phthalocyanine dispersion was applied by dipping onto the aluminum tube on which the charge transport layer had been formed, and then heat treated at 120° C. for 60 minutes to form a charge generation layer with a thickness of about 0.5 μm.

Next, the methylpolysilsesquioxane obtained in the synthesis example was completely dissolved in methyl ethyl ketone. Using this coating solution, a resin solution was applied to the aluminum support coated with the charge transport layer and charge generation layer sequentially by a dipping/pulling method, and then cured by heating to protect the surface to a film thickness of approximately 1.5 μm. A positively charged organic photoreceptor was fabricated by forming a layer.

The following measurements were performed on this photoreceptor. First, corona charging is performed at 6 kV, and the surface potential after 1 second is Vo (V). Then, the surface potential when dark decayed for 1 second is V, (V), and from that moment on, it is 780 nm, lo μm/cffl.
Perform exposure with
Calculate. Furthermore, one process is completed by recording a surface potential Vr (V) of 10 j +/□ after the start of exposure. In addition, calculate 100 X V + / Vo and calculate the charge retention rate D
I (%). The results obtained are shown in Table 1.

Next, stability during repeated use, that is, durability - 1
- In order to evaluate the properties, the properties of the photoreceptors prepared in this example were compared. The results are shown in Table 1 in comparison with the initial results.

As a result, it is clear that the photoreceptor of the example has almost no change in photoreceptor characteristics even after 100,000 printings, and has extremely excellent printing durability.

Table 1 In Examples, a charge transport layer and a charge generation layer 1 are provided on a conductive support.
Although we have given an example of using an electrophotographic photoreceptor in which surface protective layers are sequentially laminated, it is also possible to form a single-layer organic photoreceptor containing a charge-generating substance on a conductive support, and then form a surface protective layer thereon. , when forming a photoconductive layer of a single-layer organic photoreceptor containing a charge generating substance and a charge transporting substance on a conductive support and forming a surface protective layer thereon, a charge generation layer is formed on the conductive support. In any case where an electrophotographic photoreceptor is used in which a charge transport layer 9 and a surface protective layer are sequentially laminated, lower alkyl polysilsesquioxide represented by the following general formula and having a weight average molecular weight of 103 to 107 is used as the surface protective layer. It goes without saying that the sun can be used after being cured by heat.

[Effects of the Invention] As described above, the photoreceptor of the present invention can achieve durability and printing durability that were unachievable with conventional organic photoreceptors.

Agent Patent Attorney Sada Igata

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor in which a photoconductive layer and a surface protective layer are sequentially formed on a conductive support, a lower alkyl polymer represented by the following general formula and having a weight average molecular weight of 10^3 to 10^7 is used as the surface protective layer. An electrophotographic photoreceptor characterized by using heat-cured lusesquioxane. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R represents CH_3 or C_2H_5)